Monitor apparatus for blood transfusions



S. B. MAUCHEL MONITOR APPARATUS FOR'BLOOD TRANSFUSIONS May 20, 1958 2Sheets-Sheet 1 Device Filed June 6, 1955 Vem HHHD

INVENTOR S MAUCHE .m Pat ent Atiorng 1958 s. B. MAUCHEL 2,835,252

MONITOR APPARATUS FOR BLOOD TRANSFUSIONS Filed June 6, 1955 2Sheets-Sheet 2 IIIIIIIIIIIIII III/4m JNVENTOR S B. MAUCHEL United StatesPatent MONITOR APPARATUS FOR BLOOD TRANSFUSIONS Sydney Bertram Mauchel,Saskatoon, Saskatchewan, Canada, assignor of one-half to James B.McFadyen, Monrovia, Calif.

Application June 6, 1955, Serial No. 513,419 Qlaims. (Cl. 128-214) Thisinvention concerns a system for automatic monitoring of flow of fluidadministered from a container via a delivery tube into the circulatorysystem of a subject, and in particular relates to apparatus for andmethod of carrying out an intravenous transfusion incorporating meansfor guarding against introducing air or gas bubbles into a vein of therecipient.

It is essential in carrying out a transfusion of any fluid into thearterial system of a subject that gas or air be prevented from entering,since even very small amounts of air in the blood vessels may give riseto a gas embolism which would be fatal. Whenever a body fluid such aswhole blood is to be administered from a source as a blood bottle, acertain amount of froth is almost inevitably developed at the interfacebetween air occupying the space above the blood and the blood volume, sothat as the contents flow intothe delivery tube there is an ever presentpossibility that some of the small bubbles may become entrained with theblood and carried into the subjects arterial system.

In certain circumstances sterile air is applied under pressure to give apositive pressure in the flask in addition to the usual gravity headprovided to urge the flow, and the entry of such air bubbling throughpart of the blood volume tends to entrain small bubbles in the fluid.

it may be stated generally that the concept of filtering and trappingundesirable gas occlusions or other matter at some point along the Howpath of a fluid in a transfusion is one that is old in the art. Many ofthe devices realized heretofore have relied on the separation of thebubbles entrained by providing a trap chamber, wherein the velocity offlow is arranged to be slow and a gravity separation clears at least thelarger bubbles. Devices of this sort have in luded baflies and similarfeatures for deflecting bubbles to assist them to rise to the surface ofthe trap volume. Notwithstanding the efiicacy of such apparatus there isinevitably a longer set-up time, more items to be cleaned andsterilized, and waste of some fluid in the trap. Furthermore attentionmust always be given to such. additional equipment otherwise a gasocclusion could conceivably arise if the trap drains below a certainlevel.

Inasmuch as transfusion apparatus of known type and widely in usecomprises a length of delivery tube associated with which are a filterand the connectors whereby it may be attached to a blood bottle at oneend and to a blood needle at the other, the use of a trap has obviousdisadvantages. According to this invention, the flow in such deliverytube is monitored externally thereof and without requiring anyconnections, by an automatic guard whereby even very minute bubbles maybe detected and the flow arrested, such method representing a decidedsimplification and improvement in reliability over gravity type traps.

It is therefore an object of the invention to provide a means formonitoring the flow continuously and auto matically by a sensing deviceincluding a photoelectric cell and a source of light so arranged as todetect any 2 change in opacity of the fluid passing through a testportion of the delivery tube between the light source and thephotoelectric device.

The invention also provides a flow arresting device which is positiveand simple in its operation and which may be tripped from a latchedposition in response to the detection of a predetermined reduction ofopacity of the fluid, signifying the presence of an occluded 0rentrained volume of gas, to arrest the tlow by clamping the tubedownstream of the detection point.

It is also an object of the invention to provide apparatus for arrestingthe flow and holding such arrested condition until such time as anattendant has cleared the gas bubbles to a safe condition and then takendeliberate steps to restore the flow by re-latching the arrestingdevice.

Still another object of the invention is the provision of a novel andsimple analyzer into which a portion of the length of delivery tube of atransfusion apparatus may be placed or from which it may be removed witha minimum of handling.

A. further object of the present invention is the provision of a controlwhereby the sensitivity of the analyzer may be adjusted.

Yet another object is the realization of a simple safety device wherebyfailure of the lamp in the analyzer or failure of the A. C. power supplyarrests the flow of the fluid.

Referring to the drawings, Fig. 1 is a perspective view of the externalappearance of the monitor, with arrest ing, indicating, and controlelements together with a length of delivery tube in use;

Fig. 2 is a schematic block diagram of the disposition of units in theirfunctional inter-relationship;

Fig. 3 is a generalized layout diagram of the monitor in use;

Fig. 4 is an elevation view in cross-section showing the flow-arrestingclamp in latched position, and the tripping relay;

Fig. 5 shows a cross-section in elevation of the analyzer assemblycomprising a housing, lamp, lens, and photoelectric tube;

Fig. 6 is an electrical schematic diagram of the circuit of the analyzerand the fail-safe lamp circuit; and

Fig. 7 is a perspective view of the flow-arresting unit fitted with adual-finger retainer for the delivery tube.

In Fig. 1 there is shown a complete assembled guard device in a form asit would be used in a location such as an emergency ward, hospitaloperating room, or laboratory. A section of the clear plastic deliverytube 10 is shown in position, leading from a supply of blood or otherbody fluid (not shown) to be administered intravenously. The tube passesthrough an analyzer housing 11 into which it is inserted by tipping thehousing sideways about a hinge (shown in Fig. 5) and laying the tubeinto a groove. The further portion of the tube is passed under the jawor pinch 12 of a clamp unit designated generally as 13 and is restrainedby a spring finger 14 on the downstream side of the jaw. Alternatively,a dual-finger retainer 14 may be employed, as shown in Fig. 7, normallybiassed against plate37 by spring 52, and actuated by handle A trippingrelay 15 is shown in its relationship with the latch 16 of the clamp. Asupply control switch 17 is provided at the side of chassis 120, while apilot lamp 18 of distinctive colour is also mounted on the side toprovide visible indication of the energization of the apparatus. Awarning lamp 19 is mounted on the face of the chassis for the purpose ofindicating visually the tripping of the latching relay. A reset button21 is provided, whose function will be made evident as the descriptionproceeds.

In Figs. 2 and 3, a body fluid supply, here indicated as aesaaea wholeblood in blood bottle 22 of standard design, is ad ministered byintravenous injection through a delivery tube comprising the usualconnectors 23 which may be glass or plastic, 2. filter 24, and a needle25. It is to be Understood that such assembly represents a standard kitpackaged as sterile tnansfusion equipment already assembled, requiringonly to be attached to the blood bottle through the cap 26. The monitorof Fig. 1 is located along the delivery tube, preferably as near aspossible to filter element 24, and held in position as shown by thedashed outline 28 by clamp 27 supported on upright of stand 29. Thismonitor includes photocell 4s and housing 11 containing the light sourceincorporating filament 42. The stand will also be used to support clamp32 by which the blood botte is held. The delivery tube is passed throughthe analyzer unit 30 and under the jaw of pinch 12, the remainder of thetube, ordinarily some feet in length, being disposed in any mannerconvenient for the type of transfusion to be effected. A pressure tube31 through which sterile air or a suitable gas under pressure may beapplied to assist discharge of the contents is led into the bottlethrough the cap 26.

Referring to Fig. 4, the arrangement of elements forming the flowarresting unit will be described in detail. A pinch 12 extending beyonda housing 13 forms one end of a lever arm which pivots about axis 33,the other end of the lever arm carrying a spring retaining tube 34 intowhich is threaded an adjusting device 36. Spring 35 is adjustablycompressed by turning thrumbscrew 36 to produce a biassing force tendingto close the jaw or pinch 12 against the base plate 37 of the housing. Alatch device 16 normally holds the lever in the cocked position, thespring 33 and relay tending to hold the latch engaged. When the windingof relay 15 supported on chassis is energized by the application ofvoltage the armature member 39 is attracted to the core and therebymoves the latch 16 out of engagement with the lever arm, which pinchesthe tube 10. The delivery tube is held in position under the jaw bybeing gripped under the bow or spring fingers 14.

A switch 40 which is preferably a single pole double throw micro-switchis arranged to be opened when the relay operates and to transfer acircuit from one contact to the other.

The analyzer unit, shown in cross section in Fig. 5, comprises aventilated lamp housing 11 and a tube 41 slidably positionable therein,for the purpose of adjusting the distance between the lamp filament 42and lens 43. A set screw 44 may be employed to retain the tube indesired position. The analyzer includes a light gate, arranged in theform of collimating discs having apertures 45, 46, and opposedsemi-cylindrical grooves diametrically of the discs, to provide acylindrical space for receiving tube 10. A hinge joint 47 is providedbetween the discs to permit the housing 11 to be swung into an openposition, thereby enabling the tube 10 to be laid into the groove. Asuitable spring device is incorporated in any manner to tend normally tohold the light gate in closed position. The lower collimating disc issecured to the chassis 211, in registry with an aperture therein. Aphotoelectric detector device 4% which may preferably be a phototube ismounted on the under side of the chassis 20 in light receiving relationwith the collimating apertures of the light gate.

When lamp filament 42 is at incandescence, light shines on a shortlength of the tube in the light gate. Normally the phototube receivesnegligible light when blood fills the delivery tube, but the presence ofa small bubble of gas decreases the opacity and therefore increases theamount of light incident on the phototube. The action of the monitorwhen such condition is detected will now be described in detail withreference to Fig. 6. A. C.

A supply is applied to the primary of a transformer 49 through an on-offswitch 17, and energizes neon lamp 18, as well as heating lamp filament42 which is in series with a low voltage A. C. relay 50. The secondaryvoltage of transformer 49 is rectified by full wave rectifier tube asand filtered by condenser 54. While the lamp current is flowing, themoving contact 51 is held open, thereby holding off positive bias fromthe grid of the gas tube VI. Positive direct voltage is applied to theanode of phototube 48 in series circuit with resistance R6, from avoltage divider network comprising R1, R2 in series with the parallelcombination of fixed resistance R3 and variable unit R4. When thephototube detects an increase of incident illumination, the grid bias ofV1 is reduced, depending on the setting of control R4, and at a chosenthreshold value will cause the gas trigger tube to fire. Relay 15thereupon has its Winding energized and trips the latch 16, causing flowin tube 1.0 to be shut off rapidly, before the bubble or otherdisturbing occlusion has appreciably passed out of the light gate.Switch ill now transfers the D. C. positive supply voltage from therelay 15 to the warning lamp 19.

As the relay core field weakens the armature falls back, operatingswitch 40 and re-energizing the gas tube, the cycle repeating as long asthe bubble or other disturbing occusion remains in the light gate. Theoperator thereupon will take steps to clear the bubble. One method whichmay be resorted to is to apply pressure to the blood 1 tube 1% at apoint close to the pinch 12, and to squeeze the contents back throughthe light gate by sliding a finger along to collapse the tube againstthe chassis 20 up to the exit side of the housing 11. This will returnthe bubble into the filter 24 Where it may collapse or float out of theactive stream or otherwise be rendered harmless. Should it be desirableto flush the tube free of blood or fluid in which gas bubbles may beentrained, the operator has merely to hold the button 36 down while thecontents are discharged through the needle into waste.

To reset the monitor after the tube above the pinch has been cleared ofany foreign matter other than fluid,

' the reset button 21 is pressed to ensure that the gas trigger is notin circuit for the purpose of dc-ionizing the space discharge wherebythe grid circuit is restored to control. The control potentiometer R4 isturned up until the gas tube fires with the photocell dark, then thepotentiometer R4 is backed off slightly to a setting at which the tubeV1 does not fire with the tube in the light gate filled with blood. Thereset button is pressed to restore grid control of V1, and the pinch 12is latched in cocked position, whereupon transfusion may be allowed toproceed. This control in practice should not require the resettingoutlined unless it has been disturbed. If the instrument has been inoperation for a long time, it may be advisable to check the setting inthe manner described.

In the event that the circuit to lamp filament 42 should inadvertentlybecome open, which would make the monitor unsafe by making the anlyzerinsensitive, the release of relay 5t) closes the moving contact 51against the stationary contact, and in effect reduces the negative biason the control grid of V1. By a suitable choice of constants thisreduction effects the firing of the tube and arrests the flow. Shouldthe A. C. power supply fail during the use of the monitor, relay 50rapidly releases, thus closing contacts 51, which will fire V1 due tothe charge stored in the main high-voltage filter condenser Fluids moretransparent or less opaque than blood, such as plasma, glucose, andother fluids capable of being administered intravenously may also bemonitored by the device. In such case the change in opacity can berendered more easily detectable when a bubble enters the light gate, byadding a harmless coloring material, or employing a polarizing filterand analyzer on opposite sides of the delivery tube in the light path.

Tube V1 Type 2D21 Thyratron. P. E. cell 48 Type 927 phototube. Lamps 18,19 Type NE 51 neon. R1 l3 kilohms. R2, R3, R4 l0 kilohms each. RG 1Omegohms. D. C. rectifier output 250 volts.

I claim:

1. In a monitor of flow of fluid in a delivery tube, control apparatusresponsive to detection of the presence of gas bubbles in the fluid andeffective to arrest the flow thereupon, comprising an analyzer adaptedto have a portion of the length of the tube passed therethrough, asource of light, a collimating aperture disposed adjacent said length oftube to direct incidence of light upon an exterior wall area thereof, aphotocell disposed to receive such light as is transmitted through thefluid from said source, a spring-biassed clamp located downstream of theanalyzer having a jaw actuatable between a cocked or open position and atripped or closed position, said clamp being adapted to be held in theopen position by a latch, a retaining finger associated with the clampfor positioning the tube in the line of action of the jaw, a solenoidhaving an armature, a detent carried thereby and cooperating with thelatch to restrain closing of the jaw when the solenoid is de-energized,and means responsive to detection by said photocell of an increase inlight transmitted through the fluid in the analyzer to energize thesolenoid and to trip the said latch.

2. In a body fluid injection system, control apparatus effective inresponse to the detection of gas bubbles in a delivery tube for saidfluid to arrest the flow, comprising a spring-biassed clamp whereof ajaw is actuatable between a cocked or open position and a tripped orclosed position, a support for a portion of the delivery tube passingthrough the clamp to position said tube in the line of action of the jawwhereby said tube will be squeezed when the clamp is closed, a latchcarried by the clamp, a solenoid having a winding, and an armatureco-operating with the latch, said armature being actuatable between arest position corresponding to the deenergized condition of said windingat which said latch is efiective to prevent closing of the jaw of theclamp when cocked, and an alternate position corresponding to theenergized condition of said winding in which the latch is released toallow the clamp to squeeze the tube and arrest the flow, an analyzercomprising a source of light and a photocell disposed on opposite sidesof a transparent portion of the flow path upstream of the clamp,

whereby the photocell is subjected to light transmitted through thefluid from the source, and means responsive to detection by saidphotocell of a decrease in opacity of the fluid in the delivery tubewithin the analyzer to cause energization of the winding of thesolenoid.

3. Apparatus as in claim 2, wherein the means causing the energizationof the Winding includes a thyratron having the solenoid winding in theanode circuit thereof, and the photocell is in circuit relation with thecontrol grid whereby detection of a predetermined increase of lighttransmitted through the fluid causes the biasing of the control grid toa potential at which the thyratron fires.

4. In a monitor for detecting decrease in the opacity of fluid in a flowtube, an anlyzer comprising a housing, a light source within thehousing, a tunnel space through the housing adapted to receive a testlength of said flow tube, a collimating aperture in the tunnel wallbetween the light source and the space occupied by said test length, aphotocell disposed in light-receiving relation with a second aperture inthe tunnel Wall diametrically opposite of the collimating aperturewhereby to detect light transmitted through the fluid, a space dischargedevice having an ionizable filling medium and including at least acontrol grid and an anode, said control grid being associated withcircuit means determining the potential of said grid, said meansincluding the said photocell in circuit with an electrical supply andeflective in response to detection of a predetermined increase in lighttransmitted to condition the potential of said grid to fire the device,an anode load circuit comprising a solenoid winding adapted to beenergized upon ionization of the device, a spring-biassed clamp normallyclosed and located downstream of the analyzer along the tube, a lengthof flow tube disposed within the clamp, a latch carried by the clamp, adetent associated with the latch and effective in a latching position tohold the clamp open and in a release position to permit the clamp toclose, and an armature supporting the detent, said armature beingactuatable between a de-energized and an energized position by saidsolenoid to move the detent to latching and release positionsrespectively.

5. The monitor of claim 4 further including, in the circuit meansdetermining the potential of the grid, a relay arranged to be energizedtogether with the source of light from an electrical supply, a switchactuated by the relay in the energized state to a first condition torender the photocell effective to control the potential of the saidgrid, and actuated to an alternate condition when the relay is indeenergized state to substitute at said control grid a positivepotential tending to fire the space discharge device.

No references cited.

